The ANNELID system is not developed enough, and still different authors offer a different number of classes of these animals. So, the class of rings - Echihurides - now more often allocate in separate type Worms. We will look at the classification by which the rings are divided into five classes.
Type of ring worms (9 thousand species)
Class Primary rings or Dinofilids (5 OTP, 40 species)
Class Mizostomida (1 otr., 130 species)
Leech class (3 OTP., 400 species)
Class of non-timeline, or oligochettes (25-27 sections, otf. Not developed, 3.8 thousand, according to other data 5 thousand, species)
Class Multi-Point, or Polycetes (25 Otr., 7 thousand species)
First consider small classes at the rings. These are primarily Primary rings They live in sand shames. These are small animals from 2 mm to 3 cm. A more numerous class - Mizostomids. All of them live in the bodies of Icharineri ( marine stars, Officer, marine Lilies), It is completely tiny flattened animals from 3 to 30 mm long.
In the shallow water in the sand digs his minks to the worm of Peskodnod. These minks are short and curved, both of them come to the bottom surface. Perekadodil captures and swallows sand along with organic foods located among the grains of sand, - small animals, algae, lip pieces. Often it is enough for one of the ends of the fish. Then the worm rests on the walls of the mink with their bristles and part of the body breaks down, remaining in the mouth of the fish. After some time, the lost part of the body (this is usually the rear part) is restored.
The most famous from Palolo Worm Polychet. Pacific Palolo lives in coral Rifah Near Fiji Islands and Samoa. In October or November on the New Moon Day, this worm appears on the surface of the water in such quantities that water becomes opaque. In this case, the front end of the worm remains at the bottom, and the largest rear side (about 40 cm long), stuffed with mature sex cells, pops up to the surface. The local population of the islands is eagerly waiting for the reproduction time of this worm and goes to the boats to industrial. Palolo is considered delicacy in dried and fried. At a certain time, at the same time emerging parts of the worms are broken down on the side and eggs and spermatozoa flow from these wounds. In water occurs in fertilization, and the embryos are lowered to the bottom. The Atlantic Palolo lives at the Antille Islands and rises in the mass to the surface also to the new moon, but in July.
Just like Palolo, polychaetes from the family behave Neret.The name of them is borrowed from Greek mythology. From the marriage of God is spawning with the daughter of Ocean Dorida, 50 nonreid - cheerful sea nymph. They usually accompany the rulers of the seas of Neptune everywhere. Polycetes of Neread live in all seas. The body is most often painted in green tones and drops with all the colors of the rainbow. They live in Norah, which are digging in the sand. For breeding, non-rising to the sea surface, where they make a marriage dance. Females, snifferly flexing, float at the surface, and males are circling around them. From fertilized eggs appear larvae - throhfor Which 2-3 weeks fall on the bottom. Many species of these worms fishermen are used as bait for fishing fish. There is fishery of these worms for sale fishermen. Hands Usually, such a fishery is swollen and cramped with powerful jaws of defending worms. One of these worms - nonreis - acclimatized in the waters of the Caspian Sea. He was so worried there and multiplied that it was now a significant addition to the feed base of local fish.
The next class of koletsov - unauthorized worms (oligo-hate) - there is no suckling and mustache on the segments. The head department is weakly expressed. The nationic cavity is well developed, they are hermaphrodites and their development occurs without a larger stage. Systematics Oligochet is still not enough, and usually do not distinguish between the detachments. Even the number of species in different sources It differs greatly - from 3.8 thousand to 5 thousand. Live oligochetes in water and in the soil, their most different sizes: from a few millimeters to 2.5 m.
The most common representative of the oligochet of our fauna is a rainworm. The rainworms are very diverse, there are several types in medium latitudes, similar to each other. The local population of all calls them just "rainworms." The name was born due to the peculiarities of these olighats in the mass appearing on the surface of the soil during and after the rain. They chase them to the surface of the trematode larva, for which the worms are intermediate owners. The larva dospel and she needed to move to the main owner - the bird. Therefore, we have selected outwards and behave so weird, located on open unprotected and easily visible places. Why do not worms get out of dry weather? The land of the soil, the deeper the worm is in search of a wet environment, the body is wet. In the rain and on the surface there is enough damp, and worms carrying trematology, get the opportunity to appear on the surface and do not dry.
The rainworm living in Altai - Alolobofor (it is called "Salazana") it reaches a length of up to 30 cm and the thickness is up to 1.5 cm. The most common is commonly called Australian earth worm. The length of his body is up to 2.5 m with a thickness of 3 cm. In the soil, it breaks up entire holes. From afar of such a worm can be taken for large snake. South American rainwill is just as huge, no less large and soil worms that live in South Africa. All of them play a big role in the life of the soil. I pass it through my intestines, they enrich it with nutrients (mineralized), stirred soil layers. Through the moves of worms in the soil penetrates air and water. As for giant worms, they are additionally useful in human farm, since local residents I am pleased to eat them. However, they are harmful because the moves of these iligocheters are so great that by making them under the buildings, they contribute to the settlement and destruction of these buildings.
Rainy worms are long-lived organisms. The usual duration of their life is 3-4 years old, in the laboratory conditions, one of them lived 6.5, and another 10.5 years.
The oligochet, inhabiting our reservoirs, is known to all fans of the Aquariums of the worm of the tube. It dwells at the bottom of the reservoirs in thin minks, of which the rear third of the body of this worm fluctuates and wave. In this way, the tubener breathes. It makes it with the entire surface of the body, especially its rear rich blood vessels part. On the front, the submerged part is the mouth, which the worm swallows the sand with element particles all the time and other detritus, during the day it passes through the intestine a huge amount of this material exceeding the mass of his own body. So the pipes are engaged in the purification of our reservoirs.
The last class of koletsov, which we look at, - leeches. The structure of these animals is varied, the magnitude of them from 2 mm to 20 cm. The leeches do not have bristles, the outer segmentation of their body does not correspond to the inner. The body cavity (whole) in leeches was reduced and turned into a lacoon system (space between organs that do not have its own walls). In many forms, these lacuna function as blood vessels, but circulatory system disappeared. Characteristic sign leeches - availability of suckers - one or two. One suction cup is usually placed at the front end of the body and is associated with the oral hole, the second - at the rear end of the body.
Leeches - hermaphrodites, the development occurs without transformation. As a rule, these animals lead a predatory or semi-parasitic lifestyle. They live in fresh reservoirs and only a few switched to life on land. Several forms live in the seas.
A special detachment is uncomfortable, or they are also called jaws, leeches. Their representatives are also very widespread on the planet. These include all the well-known medical leeches. This is a large worm of up to 12 cm long. In the laboratory, a medical leech of almost half-meter length is grown in a heavy diet. Live medical leeches in the south of Europe. In the reservoirs of Siberia, as well as the Northern and Central Europe, they are not found. Use them for medical purposes, so they are grown for pharmacies in specialized laboratories. In nature, this leech is almost not found due to intensive fishery.
It is very similar to the medical and almost the same magnitude of another jewish leech - a large falcons. She sows horror among the swimsters of Central Europe and Siberia. Nevertheless, it is completely safe for a person, blood does not suck, stupid teeth are not able to damage the human skin. However, great and terrible is extremely extraordinarily due to similarity with its more aggressive relative. This is a predatory leech, it hunts under water in small animals of the reservoir, can eat even fry fish. Salzonskaya called it because it looks like a horse leech (it is also called Egyptian or Nile). This leech with weak jaws, who are not able to contact human skin, but nevertheless, it is an active bloodstream. It is embarrassed to the mucous membranes of a swimsuit. She has enough strength to cut these fabrics - eyes, mouth cavity, nasopharynx, sexual and posterior hole. Cattle in the countries where this leech lives, it suffers greatly from it, she is dangerous for a person. Swim in reservoirs Central Asia And the Transcaucasia where this leech lives is quite dangerous.
The last detachment, which we mention here, are prying leeches. They studied weakly. Blood these leeches are not sucking, but are active predators. In our reservoirs, small falcons leeches are widespread from the leeches of this group (nehelis is also called it). It looks very similar to a large falcons leech, but three times less than it in size. She is the most frequent victim of his larger and bloodthirsty relative. Same, small falcons leech feeds on small worms, mosquito larvae.
Control questions
- 1. What classes Anneldy are the most rich in species?
- 2. Where do polychate live?
- 3. What polycetes are used by a person, and what kind of fish are rummaged?
- 4. How many types of earthworms do you know?
- 5. Why are the worms after the rain get out of the surface? And why do they crawl into the most open place?
- 6. Do killed worms live in our reservoirs?
- 7. Where is the biggest oligochets on Earth?
- 8. How do leeches differ from other rings?
- 9. What leeches can drink blood in humans?
- 10. Whom do you know from Pullpieces?
- 11. How does ulitkova leech live in our lakes?
general characteristics
ring (segmented)
with the number of segments from several tens to several hundred
general characteristics
On each segment - parapody -
muscular grows on the body of multi-minded worms, located in pairs on each torso segment and necessary mainly as the movement organs
general characteristics
Currently, about 9,000 species are known.
Divided into 3 classes:
- Multi-singing
- Unobtinka
- Leeches
Diversity of ringed worms
Multi-piece class
- Sea views.
- Have a head with tentacles, a pair of mustache, two pairs of eyes.
- Each segment has parapody with bristles.
- Have gills.
- Separation.
Peskodnod
Diversity of ringed worms
Sea Pescape
Large worms up to 20 cm long, dwelling in U-shaped minks, which are digging in or sandy soil. Feed, flowing through the intestines bottom sediment.
Diversity of ringed worms
Large worms The length of the body of a half-green individual is usually from 4 to 10 cm, but it can reach 90 cm.
Diversity of ringed worms
Live in crevices of coral reefs. Adults are up to 45 cm long and during consideration under water resemble spaghetti.
Diversity of ringed worms
Purple Australian worm
The ring worm It can reach 3 meters in length (thickness at the same time about 2.5 cm).
Worm dwells in the tropical waters of indian and Pacific Ocean from East Africa Prior to Indonesia, Philippine Islands and even Japan.
It dwells at the bottom, usually at a depth of 6 to 40 m, mainly on coral slopes and shallow lagoons.
Palolo periodically appears in some places in the ocean, which at this time literally tends them. So, the Atlantic Palolo (Eunice Fucata), three days before last quarter The moon, in June - July, massively floods to the surface of the sea near Florida and nearby islands. Ana - including Vanuatu and Samoa - uses reproductive parts of Palolo as a source of food (just like the population of Eurasia - caviar and milk of some species of fish). During their short annual appearance at the last quarter of the Moon in October-November, worms with enthusiasm are captured by networks: they are eaten as raw, and prepare in various ways, they are harvested. This event is so important for the residents of Torres and others coral Islands Vanuatu, that it is indicated in their lunar calendar.
Diversity of ringed worms
Class of maloshetinkovye
- Soil.
- The head is not isolated.
- The senses are poorly developed.
- Parapodiy no, little bristles.
- Hermaphrodites.
- Representatives: Rainworm, tube
Rain
Tube
Diversity of ringed worms
Avcral earthworm
the largest of all famous underground invertebrates in the world. Residents of Australia very much worship their unusual neighbors. In their honor, even established the annual international festival "Karmai" (the name of the worm on the adctor of local aborigines).
Value
Mix humus, contribute to the decomposition of the puff, ensure access to the soil of oxygen
Feed base for carnivorous animals
Diversity of ringed worms
Medical
leech
Flaskonskaya
leech
Value
The leeches produce a girudine that prevents blood coagulation and promoting thrombus resorption.
Use in medicine.
1. Mature of ringworms in nature.
Freshwater worm-tubes, forming numerous settlements at the bottom of the reservoirs include freshwater worms. Some tubes take an active participation in the biological treatment of water bodies. Water oligochettes are a favorite food of many fish.
Multi-point worms inhabit the seas, upholstered both in shallow water and at considerable depths. Neread lead the bottom lifestyle, moving with parapodies along the bottom. Some can float, rising to the surface of water during the breeding period. Ponkzozhili inhabit sandy shames, deeply burling into the ground, laying the moves with the help of a strongly developed musculature of the body.
2. Building and biology rainworm.
Rainworm is a typical representative of young-skinned worms living in the soil. These animals Поколо клюбольный молноги, partially pushing the soil with muscle movements of the body, partially swallowing. The mooring of life was reflected in their external structure. The head department is expressed weakly, the supreets, eyes and parapodies are not. On numerous segments of the body are small so-tinki, with the help of which the worm rests on the walls of the pro-rich stroke. Therefore, pull it out of the mink is very difficult. In the skin of a rainwater worm of a lot of glands. The abundance of mucus secretions protect the skin from drying, mechanical damage, facilitate movement in the ground and contribute to breathing. Blower rainworms of leather, in which the thick network of capillaries is located. They feed on rotting plant residues, passing the mass of the earth through the digestive tract. The digestive SIS-topic is divided into mouth, a throat, a thin esophagus, goiter, a muscular stomach, a long intestine with a longitudinal and frontal phenomenon. All other organs of organs have a typical structure for ringeled worms. Rain worms hermaphrodites. Fertilization cross. In the excreted individuals in the anterior third of the body, a jelly-zhysty-bearing belt develops, which, during the ripening of the egg, it highlights a thick mucus forming a flour. Reducing the body of the worm shifts it to the front end. During movement in the faucet, eggs and sperm-zoids are highlighted. After the clutch clenches from the body of the worm, it turns into a cocoon with fertilized eggs. Through some of the eggs develop small worms from eggs. Thus, the development is direct, without turning.
Rain Cerves play an important role in raising soil fertility. Roy Minka, they improve its structure, loose, enrich organic substances, it will be promoted by aeration and penetration of moisture, stimulate the pro-traverse nitrification.
3. The overall characteristics of round worms. Material from site.
The central group of this type is the class of round worms (nematodes), one of the most numerous classes of the wage kingdom. Among the nematode there are both free-living and parasitic species. Free-lived meet in all fresh water bodies, in the seas and oceans, many among nematodes and soil forms. Parasitic species will also settle in plants, and in animals, and in Checkle. For all round worms, a non-grinded te-lo, covered with a dense shell - cuticle. Under the cuticle there is a modified epithelium - kinderma, under which one layer of longitudinal muscles lies. The feature of round worms is the presence of a primary body cavity formed by the decay of parenchyma, which filling the gaps between internal organs At the ancestral forms. The body cavity is filled with a liquid and you are full of important functions: reference (as the liquid is under pressure, it supports the skin-muscular bag and gives the body a certain form), transport, protective. The nervous system consists of an eye-lobel ring, from which the nervous trunks are departed - the dorsal, abdominal, side. Sensivities are poorly developed: there are organs of touch and chemical feeling. In the digestive system, the rear part of the intestine with anal hole appears for the first time, so the pity-the-rectuate path becomes through. In nematode, the allocation authority is one big cage With excretory channels - cervical iron. No blood and respiratory systems. In parasites, breathing anaerobic. Round worms separatogs, part with severe sexual dimorphism. Development occurs with metamorphosis.
Ring Worms - bilateral-symmetrical segmented animals.
Systematics. Type includes 5 classes, of which the most famous Classes of Multi-Point (Polychaeta) - 13,000 species, unobtinka (Olygochaeta) - 3500 species and leeches (Hirudinea) - about 400 species.
Body shape and sizes. The body of the rings in the overwhelming majority is worm-like, in cross section round or oval. The body has a pronounced both external and internal segmentation. In this case, they are talking about true metamery. In this case, the metameter applies to the internal structure of worms. In leeches, the outer segmentation does not correspond to the inner.
The dimensions of the ring worms range from several millimeters to 2 m (ground forms) and even up to 3 m (sea views).
External structure Body. Multi-playing is well expressed by a head department, carrying a variety of destination: tentacles, eyes, palpses. In some species, palpates are growing into a complex catcher. On the last segment there are one or more pairs of sensitive mustache. Each torso segment on sides carries parapody - complex body grows. The main function of these growing is the movement of the worm. Each parapody consists of two blades, within which there are numerous bristles. Of these, they are somewhat larger, they are called acycles. A pair of sensitive mustache is attached to the blades. The composition of parapody often includes a gill apparatus. Parapody have a rather diverse structure.
In unauthenetinkic worms, the head unit is taller, the side grows (parapody) are absent. There are only relatively few bristles. On the body, the "belt" is noticeable, consisting of thickened segments.
The leeches in the front and rear end of the body are powerful suction cups. Few species on the sides have gill growing.
Skin-muscular bag. Outside, the body of ringed worms is covered with a thin cuticle, under which the cells of the skin epithelium are lying. Skin of worms is rich in ferrous cells. The secret of these cells has a protective value. In a number of species, skin seals go to the construction of peculiar houses. Bristles of worms are epithelium derivatives. A layer of ring musculature occurs under the skin, allowing the animal to change the transverse body size. Below are the longitudinal muscles serving to change the length of the body. The leeches between the layers of ring and longitudinal muscles are located a layer of diagonal muscles. The rings have special muscles, leading in motion of parapody, palp, suction cups, etc.
Body cavity. The space between the body wall and the internal organs in the rings represents the whole - secondary body cavity. From primary it is distinguished by the presence of own epithelial walls, wearing the name of the nodium epithelium (target). Siftles covers the longitudinal muscles of the wall of the body, intestines, muscle trash and other internal organs. On the walls of the intestine, the solar cells are converted into chlorogenic cells that perform an excretory function. At the same time, the nominal bag of each body segment is isolated from neighboring partitions - dissertes. Inside the nominal bag is filled with a liquid containing various cell elements. Overall performs different functions - support, trophic, excretory, protective and others. The leech has a major reduction and the space between the body wall and the internal organs are filled with a special tissue - mesenchima, in which the whole is stored only in the form of narrow channels.
The middle intestine has a shape of a simple tube that may become more complicated. So, the leeches and some multish intestines have lateral growth. In the dish, on the spinal sides of the intestine there is a longitudinal fold, which deeply goes into the cavity of the intestine - Typhlosol. These devices increase significantly interior surface Middle intestine, which allows you to most fully assimilate digested substances. The middle intestine has an entodermic origin. Unabroad worms at the front and mid-intestine border there are expansion - stomach. It can be both ectodermal and entodermal.
The rear, which is the derivative of Etoderma, is usually short and opens with anal hole.
Circulatory system Killed worms are closed, that is, the blood is moving everywhere along the vessels. The main vessels are longitudinal - spinal and abdominal connected by ring. The spinal vessel has the ability to ripple and performs the heart function. Oligochet this function is performed by annular vessels of the front of the body. On the spinal vessel, the blood moves back in the back. According to the ring vessels located in each segment, the blood goes into the abdominal vessel and moves in front of it back. Smaller departs from the main vessels, and they, in turn, are branched on the smallest capillaries, carrying blood all the fabrics of worms. Vehives have a system of blood vessels significantly reduced. Blood moves along the sinus system - the remnants of the aim.
The blood of most ringed worms contains hemoglobin. This allows them to exist in conditions with a slight content of oxygen.
Special breath organs Usually no, so gas exchange occurs through the skin by diffusion. Multi-point worms and some leeches have well-developed gills.
Selective system Most often represented by metanephrides, which are metairly located, that is, in pairs in each segment. Typical metanephridium is represented by a long sore tube. This tube begins the funnel, which opens as a whole (secondary body cavity) of the segment, then it permeates the partition between segments (dissipive) and enters the ferrous metanephridial body, located in the next segment. In this gland, the tube is strongly wriggled and then opens separating sometimes on the side surface of the body. The funnel and tube are covered with cilia, with the help of which the stripe fluid is rushed into metanephridium. When moving along the tube through the hardware from the liquid, water absorption and various salts occurs, and only products to be removed from the body (urine) remains in the cavity of the tube. These products are displayed through an excretory time. In many species in the rear section of the metanephridial tube there is an extension - bladderin which urine is temporarily accumulated.
Primitive colliding worms of allocation organs, like flat worm, arranged in type Protonfridiyev.
Nervous system It consists of a regulatory ring and the abdominal nervous chain. Above the throat is a powerful-developed pair complex Ganglia, representing a kind of brain. A pair of ganglia is also under the throat. The brain is connected to the fading ganggia nerve hollows covering the throat from the sides. All this formation is called a regchloride ring. Further, in each segment under the intestine there is a pair of nerve ganglia, which are connected both among themselves and with ganglias of neighboring segments. Such a system is called the abdominal nerve chain. From all ganglia nerves to various organs.
Sense organs.On the head unit of multi-minded worms there are well-developed senses: mustaches and palp (touch), eyes (sometimes quite complicated), olfactory pits. Some forms have developed equilibrium authorities - states. On the lateral growing of the body (parapody) there are amplifies that perform a tactile function.
At the unobtinka worms, the senses are developed much weaker than that of multi-minded. There are organs of chemical feelings, sometimes - tentacles, stavocists, weakly developed eyes. In the skin scattering a large number of photosensitive and tactile cells. Some tactile cells have a pintic.
The leeches in the skin dispelled many sensitive cells, there are always eyes and chemical feelings (taste buds).
Sex system . Among the ringed worms are available both hermaphroditic and separation forms.
Multi-singing worms in most separately. Sometimes there is a sexual dimorphism. Sex glands (gonads) are formed in a nuclear epithelium. This process usually occurs in the rear segments of the worm.
In unobtinka worms, hermaphroditism is more common. Fire glands are usually located in certain segments of the front of the worm. Comparatively small men's sex glands (semenks) have output ducts, which serve either modified metanephrides, or channels separated from them. Large female sex glands (ovaries) have ducts, which are modified metanephridia. For example, when the ovary is located in the 13th segment, the female genital holes open on the 14th. There are also seed recipients, which are filled during the mating with spermatozoa of another worm. Leeches are mostly hermaphrodites. Tsemenniki are metairo, ovaries one pair. Feeding in leeches occurs by sharing between sperm partners.
Reproduction. Ring worms inherent big variety Forms of reproduction.
Miscellaneous reproduction is characteristic of some distinct and unauthorized worms. At the same time, there is either strobeing or lateral kinding. This is a rare example of an extreme breeding among high-organized animals in general.
With sexually reproduction of multigremal individuals, containing mature gonads (epitial) transfers from a crawling or sedent lifestyle to a floating. And in some species, sex segments in ripening games can even break away from the body of the worm and conduct an independent floating lifestyle. Gamets fall into the water through body wall breaks. Fertilization occurs either in water or in the epitial segments of female.
The reproduction of non-drugs begins with cross-fertilization. At this time, two partners are applied to each other with abdominal sides and exchange sperm, which falls into seeds. After which partners are diverged.
In the future, the belt is distinguished by a heavy mucus, forming a clutch around the belt. In this clutch, the worm posts eggs. When shifting the clutch, it passes by the holes of the seeds; At this point, the enemy fertilization occurs. When the coupling with fertilized eggs slides from the head end of the worm, the edges are closed, and the cocoon is obtained, in which further development occurs. Rain worms cocoon contains usually 1-3 eggs.
Vehives, reproduction occurs approximately, as well as non-drug worms. Cocons leeches are large, reaching in some species 2 cm long. In the cocoon is different species From 1 to 200 eggs.
Development. The zygotes of ringed worms undergoes complete, usually uneven crushing. Gasastulation occurs by invagination or epibolia.
Multi-point worms in the further of the embryo is formed by a larva, called Trohforo. It has cilia and pretty mobile. Their this larvae is consequeled and an adult worm develops. Thus, most of the most distinguished worms development is coming with metamorphosis. Known species and direct development.
Unavythinkic worms have direct development without a phase of the larvae. From eggs are completely formed young worms.
The leeches from eggs in the cocoon are formed peculiar larvae, which float in the cocoon liquid with the help of the ciliary apparatus. Thus, adult leech is formed by metamorphosis.
Regeneration.For many ringed worms, the developed ability to regenerate lost parts of the body is characteristic. In some species, a whole organism can recover from several segments. However, leeches regeneration is very weak.
Food.Among the multi-minded worms are found both predators and vegetative species. The facts of cannibalism are also known. Part of the species are powered by organic residues (Detritophages). Unavythinkic worms are mostly childhood, but predators are also found.
Unavythorn worms mostly are solar inhabitants. In rich in humus, the number, for example, worms Enchitreid reaches 100-200 thousand on square meter. It is inhabited by unauthorized, they are also in fresh, saltwateled and salted water bodies. Water residents Inhabited mainly surface layers of soil and vegetation. Part of the species - cosmopolitans, there are endemics.
Vehius inhabit fresh reservoirs. Few species dwell in the seas. Some switched to a terrestrial lifestyle. These worms lead either an appeal lifestyle, or actively wanted their owners. Single bloodsucked providing leeches of food for many months. Among leeches there are no cosmopolitans; They are confined to certain geographical zones.
Paleontological finds Ring worms are very few. Large variety in this regard is multi-minded. Not only prints are preserved from them, but in many cases the remains of the tubes. This foundation assumes that all major groups of this class have been presented in Paleozoa. Of reliable remnants of unauthorized worms and leeches have now been detected.
Origin.Currently, the most believable hypothesis of the origin of the ring worms from the parenchymal ancestors (ciliated worms). The most primitive group is considered to be multigrem. It is from this group that it is most likely to be the origin of unauthorized, and a group of leeches has been distinguished from the latter.
Value.In nature, ringed worms have great value. Inhabiting various biotopes, these worms are included in numerous food chains, serving a huge amount of animals. Ground worms play a leading role in the soil formation. Processing plant residues, they enrich the soil with mineral and organic substances. Their moves contribute to the improvement of the gas exchange of the soil and its drainage.
IN practical plan A number of rainworm types are used as biohumus manufacturers. Worm - enhitra used as feed for aquarium fish. Enchitreyev breeds in huge quantities. For the same purpose, the worm of the pipeline is mined. Medical leech Currently use for therapy of certain diseases. In some tropical countries, we use food palolo. - sex (epitocal) worms segments separated from the front of the animals and surfaced to the surface of the water.
General Characteristics of the type of arthropod.
Art-legged - double-sample-symmetric segmented animals with metairly arranged segmental limbs. This is the richest and diverse group of animals.
Systematics. The type of segregate is divided into several subtypes.
Subtype of the landscraft (crustacean class)
Subtype trilobitis (extinct group)
Subtype Helisser (class Merostovaya, Class of Poworkoons)
Subtype primary meter
Subtype trachekins (Multicacker class, insect class).
To the class of merciless belongs to modern skovyvosts and extinct rakoskorpions. To the subtype Primary meters These are small (up to 8 cm) tropical animals, which in structure occupy an intermediate position between ringed worms and arthropods. These groups of animals will not be considered here.
Body sizes. The body length of arthropods ranges from 0.1 mm (some pliers) to 90 cm (swords). Ground arthropods reach 15-30 cm. The scope of the wings of some butterflies exceeds 25 cm. Extincting cancer reached 1.5 m lengths, and the wingspan of the wings of fossil drags reached up to 90 cm.
External structure. The body of most arthropods consists of heads, chest and abdomen. The listed departments include a different number of segments.
HeadThe segments of which are connected motionless, carrying oral organs and senses. The head is movable or still connected to the next chest department.
Chest department Walking on behalf of the wage limbs. Depending on the number of breast segments of the limbs may be miscellaneous number. Insects also attached wings to the chest. Breast segments are connected to each other movably or motionless.
Abdomen It accommodates most of the internal organs and consists most often of their several segments, moving together. The trouser can be the limbs, and other appendages.
The river apparatus in arthropods is very difficult to arrange. Depending on the power supply, it can have the most diverse structure. Parts oral apparatus For the most part, there are strongly modified limbs adapted to use almost any food. The device may include 3-6 pairs of limbs.
Covers. Cuticle, consisting of chitin, is a derivative of immersed epithelium - hypoderma. Hitin performs a reference and protective function. The cuticle can be soaked with calcium carbonate, when it becomes a very strong shell, as it happens, for example, in crustaceans. Thus, in segmental covers of body poverty outdoor skeleton. The rolling connection of solid areas of the cuticle is ensured by the presence of a webbed sections. The cuticle of arthropods is not elastic and cannot stretch in the process of growth of animals, so they periodically dump the old cuticle (linen) and until the new cuticle has hardened, increase in size.
Body cavity. In the process embryonic development Cleanistic bags are laid by nominal bags, but in the future they break and their cavity merge with the primary cavity of the body. So the mixed body cavity is formed - Mixcell.
Musculature represented by individual muscle beams that do not form a solid muscular bag. Muscles are attached to both directly to the inner wall of the body segments, and to the inner of their processes constituting the inner skeleton. Musculature in arthropods transverse.
Digestive system In arthropods B. general It consists of the front, middle and rear intestinal. The front and rear department was lined with a thin chitinular cuticle. Depending on the type of power, the bowel structure is extremely varied. Opened in the oral cavity salivary glandswhich very often produce a number of enzymes, including digestive. Anal opening opens, as a rule, at the rear end of the body.
Selective system In primary arthropod (crustaceans) is represented by special glands located in the head part of the body. The ducts of these glands are open at the base of the antennas (mustache). Ground arthropods have a sedentary system represented by the so-called malpigiyev vessels - tubes that are blindly closed from one end, and another end is opening into the intestine on the border of the middle and rear sectors. These tubes are placed in the body cavity, and, washed by hemolymph, absorb decay products from it and bring them into the gut.
Respiratory system It works quite diverse. In crustaceans there are real gills. They are branched grows on the limbs covered with thin chitinular cuticle through which gas exchange occurs. Some crustaceans adapted to live on land (for example, wets).
Spiders and scorpions respiratory authorities are presented last lungsthat open outward holes (stigmas). Inside the pulmonary bag has numerous folds. Besides light bag Some spiders have a trachean tubing system that are practically not branched.
At ticks, multi-pool and insects respiratory system Presented trachemeaswhich open out openings (breathaf, stigma). The tracheas are very branched and penetrate into all organs and fabrics. The trachea has a thin chitin dillery and is reinforced from inside a chitinic spiral, which does not allow the tube to fall. In addition, flying insects have extensions - air bumps filled with air and reducing specific gravity Animal. Ventilation in the trachean system is underway both passively (diffusion) and actively (change in the volume of the abdomen).
Some insect larvae have special respiratory authorities - tracheal gills. Gas exchange in such arthropods occurs by diffusion.
In some ticks, the respiratory system is absent, and gas exchange goes through the entire body surface.
Circulatory system All arthropods unlucki, that is, not everywhere blood flows by vessels. Under the chitin cover of the back there is a heart from which blood vessels depart. However, at some distance from the heart of the walls of the vessels disappear, and the further path of the blood is performed on the slots between the internal bodies. Then she gets into the heart through the holes, which are called oct. In crustaceans and ticks, the heart bags, and in scorpions, spiders and insects it is multi-chamber. In some ticks, the circulatory system may be absent.
The blood from the overwhelming majority of arthropods is colorless and is usually called hemolymph. This is a rather complicated liquid: it consists of both blood and stripped liquid. Due to the lack of special pigments, hemolymph practically cannot actively participate in the gas exchange process. Hemolymph some insects (leaf outdoors, god's cows) Contains pretty toxic substancesand can play a protective role.
Fat body. Ground arthropods have a sparkling body - a fat body located between the courses. The fat body takes part in the regulation of water exchange.
Nervous system. In the general case in segmental nervous system Built by the type of ringed worms. It consists of a paired pumping gangulia, a windowless nervous ring and an abdominal nervous chain. Peripheral nerves depart from ganglia chain. Special Development It reaches the headlift gangulia in insects, which are usually referred to about the presence of a brain. The concentration of abdominal nervous chain ganglia is often observed and education due to their fusion of large nerve nodes. Such a concentration is often associated with a decrease in the number of segments (merging them between themselves). For example, in ticks, lost segmentation, the abdominal chain turns into a common nervous mass. And in many-name, the body of which consists of a variety of identical segments, the nervous chain is very typical.
Sense organs Most arthropods achieve high development.
Activities Located on the head and are often represented by complex (facetile eyes), which occupy most of the insects most of the surface of the head. Many crustacean facets are sitting on stalks. In addition, insects and spider-sized eyes have simple eyes. Unpack front eye is characteristic of some crustaceans.
Touch bodiesposted by various bristles and hairs located on the body and limbs.
Obligations and taste. Most of The olfactory expirations are located on the mustache and jaw pepons of insects, as well as on the antennok crustaceans. The smell of insects are developed very well: 100 pheromone molecules per 1 cm 2 air highlighted with a silkworm female so that the male began to search for a partner. Insect taste organs are located both on the mouth limbs and end-segment legs.
Equilibrium authorities. In crustaceans, the stavocist is in line with a major segment - the cutyriculum indulgent, seated from the inside with sensitive hairs. In this cavity, small grain grades are usually located, playing the role of Staticites.
Hearing organs. Some insects are well developed so-called tympanal organs that perceive sounds. For example, for grasshoppers they are located on the grounds of the heads of the front legs. As a rule, those insects that are capable of perceiving sounds are also able to publish them. These include many straight broken, some beetles, butterflies, etc. For this, insects have special devices located on the body, wings and limbs.
Spinning glands. For some arthropods, the presence of spinning glands is characteristic. They have spiders in the trouser and open by spider warts at the tip of the abdomen. Spiders use their web most often for hunting and building shelters. This thread is one of the most durable in nature.
In the larvae of a series of insects, spinning glands are located in the front body of the body and open near the oral hole. Their web is mostly to build a shelter or cocoon.
Sex system. Arthropods are separate animals, which are very often inherent in sexual dimorphism. The males differ from females brighter and often less than magnitude. The males insect mustache are much stronger.
Sex system females It consists of glands, eggs and vagina. Here are the apparent glands and seed. From the outer organs may be there an eggland of various buildings.
W. males The reproduction bodies are represented by seeds, enduring ducts and pressing glands. A number of forms have different organized copulation authorities.
Polymorphism. In the colonies of public insects there are individuals, differing from each other in structure, physiology and behavior. In the nests of bees, ants and termites are present, as a rule, only one female, capable of laying eggs (uterus or queen). The males in the colony are present or constantly or appear as the stock of spermatozoa from the previous mating is exhausted at the uterus. All other individuals are called workers who are females with oppressed sexual function. Termites and ant workers are divided into castes, each of which performs a specific function (collection of food, nest protection, etc.). The appearance in the nest of males and full-fledged females is only at a certain time.
Biology of reproduction. As already mentioned, arthropods are separate animals. However, among them there are cases of parthenogenesis (Tly, Daphneia). Sometimes pairing is preceded by a courting ritual, and even the fights of males for the female (at the deer beetles). After mating, the female sometimes eats the male (mantis, some spiders).
Most often, egg layout occurs in groups or one. In some arthropods, the development of eggs and larvae occurs in the organism of female. In these cases, there is a lifestyle (scorpions, some flies). In the life of many species of arthropods, there is a concern for the offspring.
Fertility arthropods fluctuate in very wide limits and depends very often from environmental Conditions. In some colors, for example, the females are laid out only one winter egg. The uterus of a honey bee is able to postpone up to 3000 eggs per day, and the uterus of termites up to 30,000 per day. For their lives, these insects postpone millions of eggs. In the medium, fertility is several dozen or hundreds of eggs.
Development. In most arthropods, development occurs with metamorphosis, that is, with the transformation. A larva is out of the egg, which, after several Linene, the larva turns into an adult animal (imago). Often the larva is very different from Imago both in structure and in a lifestyle.
In the development cycle of a number of insects is present phase dolls (butterflies, beetles, flies). In this case, talk about complete metamorphosis. Others (Tli, dragonflies, bugs) there are no such phase, and the metamorphosis of these insects is called incomplete.
Some arthropods (spiders, scorpions) are direct development. In this case, quite formed young animals come out of the eggs.
Life expectancy Arthropods are usually calculated by several weeks or months. In some cases, development is delayed for years. For example, the larvae of May beetles are developing about 3 years, deer beetles - up to 6 years. The cycade larvae live in the soil up to 16 years and only after that turn into adult cycades. The larvae of the pivots live in reservoirs of 1-3 years, and the adult insect lives only a few hours, for which he has time to mate and postpone the eggs.
Distribution and ecology. Representatives of the type of arthropods are found in almost any biotope. They are found on land, in fresh and salted water bodies, as well as in the air. Among arthropods there are both widespread species and endemics. To the first one can take a butterfly of cabbage whitening, raffs - Daphny, soil ticks. Endemic species include, for example, a large and very beautiful butterfly bramawhich is found only in the colchidal lowland.
The spread of individual species limit various environmental factors.
Of abiotic factors The most important are temperature and humidity. Temperature limits of active existence of arthropods lie in the range from 6 to 42 ° C. With a decrease in or increasing the temperature, the animals flow into the stupor state. Different phases of the development of arthropods are in different ways tolerated temperature fluctuations.
The humidity of the medium also largely determines the possibility of existence of arthropods. Excessive low humidity Wednesdays, as well as high, can lead to death. For water arthropods, the presence of liquid moisture is prerequisite For active existence.
On the distribution of arthropods big influence Provides I. human activity (anthropogenic influence ). Changing environmental conditions leads to a change species composition. As a result of the industrial and agricultural activities of a person, some species disappear, while other species are extremely breeding, becoming pests.
Origin. Most researchers converge in the fact that arthropods occurred from the ancestors close to the ringed worms. It is assumed that crustaceans, Helicer and extinct trilobites occurred from the rings with one general root, and multi-peas and insects - others.
Paleontological material on arthropod is very extensive. Thanks to the chitinium cuticle, their residues are well saved in the petrified form. Extremely well preserved ground arthropods and in amber. However, despite this, accurately trace the evolution of arthropods. It is difficult: remote ancestors of arthropods in geological layers are not preserved. Therefore, the main methods of studying this issue are comparative anatomical and comparative-embryological.
In human practical activity, it is customary to distinguish useful and harmful views.
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